Electrolytic deposition of copper



nited States Patent fi fl 1,742,412 k I "Emmomm DEPOSITION on corral: Rolf Cransberg and Hendricus Andreas Van Dusterhout, Loosdrecht, Netherlands, assignors to N. V.

" Metallic Industry, Loosdrecht, Netherlands, a limited liability company of the Netherlands No Drawing. Application April 13, 1953,

Serial No. 348,582

Claims priority, application Netherlands July 5, 1952 8 Claims. (Cl. 204-52) The electrolytic deposition of copper is an operation which is applied very frequently in the metal industry and is carried out either to embellish the surface of the treated objects, or to increase the corrosion resistance thereof, while the electro-deposited copper also serves as a base for a further treatment such as the electrolytic ers mostly do cover the unevennesses in the metal surface but do not fill them up, so that they, although lustrous, yet remain visible. The acid copper bath in so far makes a favorable exception that it has some filling action, but the copper baths proposed up till now do not have the combination of an excellently filling activity and the capacity of depositing a lustrous, soft copper layer.

From the U. S. P. 1,903,860 it is known to add thiourea or a water-soluble derivative of thiourea, such as methyl thiourea, to metal baths. These baths, however, have the drawback that the copper coating which is precipitated from the copper baths thus prepared is very hard, so that it easily springs off on bending and moreover has a very small lustrous range. Also the action of a copper bath exclusively containing thiourea as an organic compound very rapidly decreases.

From the U. S. P. 2,462,870 it is known to add thiourea and molasses to an acid copper bath from which bath, however, a copper precipitate with an entirely insuflicient lustre is obtained.

It has now been found that a soft copper layer is obtained if the combination of a substance selected from the group consisting of thiourea and a water-soluble derivative of thiourea, and a water-soluble di or trivalent alcohol is added to an acid copper bath. The bath thus prepared displays'moreover an excellent filling capacity and has a very high lustre, while the adherence to the base also is very good. I According to the invention objects, particularly metal objects, are .electrolytically provided with a copper deposit with the aid of an acid bath by using a bath containing the combination of a substance selected from the group consisting of thiourea and the water-soluble derivatives of thiourea, and a substance selected from the group consisting of the water-soluble di or trivalent a1- cohols. and the water-soluble derivatives thereof.

The invention extends to the preparation of an acid copper bath containing the combination of a substance selected from the group consisting of thiourea and the water-soluble derivatives of thiourea, and a substance se- 2,742,412 Patented Apr. :17," 1956 di and trivalent alcohols and the water-soluble derivatives thereof, as-well as the objects electrolytically provided with a copper layer with the aid of the bath. Of the water-soluble di or trivalent alcohols which are used in the acid copper bath in combination with thiourea or a water-soluble derivative of thiourea, glycerol is preferred, while ethylene glycol monoethyl ether and diethylene glycol monobutyl ether as derivatives of the bivalent alcohols ethylene glycol and diethylene glycol are preferred, because the former of these two com pounds very much improves the adherence to the base and the latter excells by the combination of lustre and filling up capacity of the bath. Of the thiourea derivatives used in combination with the di or trivalent alcohols, particularly allylthiourea and acetyl thiourea are preferred, while thiourea itself, if possible, still exceeds in activity these two derivatives.

The invention is elucidated by the following exam ples':

Example I An acid copper bath of the following composition was prepared:

CuSOaS aq g./l 150 H2504 g./l 15 Ammonium sulphate g./l 15 Thiourea mg./l. 10 Glycerol mg./l 95 An iron tube with a length of 2 dm. and a diameter of 1.75 cm. was arranged as the cathode after a pretreatment in a cyanidic copper bath in the above described acid copper bath which had a temperature of 30 C. As the anode a copper bar was used. The cathode current density was adjusted at 8 a./dm. and after 20 minutes 32 of copper had deposited on the surface. The copper layer was soft and adhered excellently to the base and the scratches originally present on the surface had practically disappeared. Moreover the surface obtained was lustrous.

Example II To the acid copper bath of Example I instead of the thiourea as much allylthiourea and instead of the glycerol mg./l. ethylene glycol monoethyl ether were added. A similar tube as in Example I was electrolytically provided with a copper layer in this bath. The

properties of this bath in broad outlines corresponded to those of the bath according to Example'I, but the lustre was still better than that obtained with the bath of Example I. Y

Example III sulfate, sulfuric acid, a brightener in a proportion of 5- 50 mgQ/liter, said brightener being selected from the group consisting of thiourea, allylthiourea and acetyl thiourea, and a filler selected fromthe group consisting of glycerol, glycol, ethylene glycol mono ethyl ether and diethylene glycol mono butyl ether.

2. A bath according to claim 1, wherein said bright- V ener is thiourea.

'3. A bath according to claim 1, wherein said brightener is allylthiourea.

glycerol.

6. A bath according to claim 1-,v wherein said filler is.

ethylene glycol mono ethyl ether.

7. A bath according to claim 1, wherein said filler is diethylene glycol mono butyl ether.

8. A bath according to claim 1, wherein said filler is glycol.

References Cited in the file of this patent UNITED STATES PATENTS Brown Nov. 20, 1945 Beaver Dec. 18, 1945 Keller Mar. 1, 1949 Avallone et al. June 7, 1949 

1. A BRIGHT COPPER PLATING BATH COMPRISING COPPER SULFATE, SULFURIC ACID, A BRIGHTENER IN A PROPORTION OF 550 MG./LITER, SAID BRIGHTENER BEING SELECTED FROM THE GROUP CONSISTING OF THIOUREA, ALLYLTHIOUREA AND ACETYLTHIOUREA, AND A FILLER SELECTED FROM THE GROUP CONSISTING OF GLYCEROL, GLYCOL, ETHYLENE GLYCOL MONO ETHYL ETHER AND DIETHYLENE GLYCOL MONO BUTYL ETHER. 